In a plasmid transformation, what is the role of an antibiotic resistance gene?

In a plasmid transformation, what is the role of an antibiotic resistance gene?

• A. It enables replication of the plasmid
• B. It encodes a fluorescent protein for screening
• C. It improves plasmid stability in cells
• D. It serves as a selectable marker so only cells that have taken up the plasmid survive on antibiotic-containing plates

Answer: (D)

In plasmid transformation, the antibiotic resistance gene acts as a selectable marker. After introducing the plasmid into cells, only those that have taken up the plasmid and express the resistance gene can grow on plates containing the antibiotic. The antibiotic kills cells without the plasmid (or without functioning resistance), so surviving colonies indicate successful uptake and expression. The other roles described—enabling replication via the origin, signaling with a fluorescent reporter for screening, or improving stability—are not the function of the resistance gene.

In plasmid transformation, the antibiotic resistance gene acts as a selectable marker. After introducing the plasmid into cells, only those that have taken up the plasmid and express the resistance gene can grow on plates containing the antibiotic. The antibiotic kills cells without the plasmid (or without functioning resistance), so surviving colonies indicate successful uptake and expression. The other roles described—enabling replication via the origin, signaling with a fluorescent reporter for screening, or improving stability—are not the function of the resistance gene.